1. Field of the Invention
The present invention relates to a hot isotropic pressure device.
2. Description of the Related Art
A HIP method (a pressing method using a hot isotropic pressure device) is used to treat a subject treatment material such as a sintered product (ceramics or the like) or a casted product at a high temperature equal to or higher than a recrystallization temperature under a pressure medium gas of an atmosphere set to a high pressure of several tens to several hundreds of MPa, and has a feature that air pores remaining in the subject treatment material may disappear. For this reason, in the HIP method, it is verified that there are effects such as improvement in mechanical characteristics, a reduction of a variation in characteristics, and improvement in yield rate. Accordingly, nowadays, the HIP method is widely used in the industrial field.
Incidentally, there is a strong demand for promptly performing the treatment in the actual manufacture site. For this reason, it is necessary to perform a cooling step requiring time in a short time among the steps of the HIP treatment. Therefore, in the existing hot isotropic pressure device (hereinafter, referred to as a HIP device), various methods have been suggested in which a cooling speed is improved while evenly heating the inside of a furnace.
For example, US 2011/165283 discloses a HIP device including: a gas impermeable inner casing which is disposed inside a high-pressure container accommodating a subject treatment material so as to surround the subject treatment material; a gas impermeable outer casing which is disposed so as to surround the inner casing from the outside; and a heating unit which is provided inside the inner casing and forms a hot zone around the subject treatment material. In the HIP device, the inside of the inner casing is formed as the hot zone, and an isotropic pressure treatment is performed on the subject treatment material using a pressure medium gas stored inside the hot zone which is adiabatically maintained by the inner and outer casings.
In the HIP device, a first cooling unit and a second cooling unit are provided as cooling units which cool the inside of the hot zone (the subject treatment material) by circulating the pressure medium gas inside the high-pressure container.
That is, the first cooling unit performs a cooling operation by circulating the pressure medium gas along the first circulation flow, and the first circulation flow is used to guide the pressure medium gas guided between the inner casing and the outer casing from the lower side to the upper side to the outside of the outer casing at the upper portion of the outer casing, to cool the guided pressure medium gas while being guided along the inner peripheral surface of the high-pressure container from the upper side to the lower side, and to return the cooled pressure medium gas between the inner casing and the outer casing at the lower portion of the outer casing.
The second cooling unit performs a cooling operation by circulating the pressure medium gas along the second circulation flow, and the second circulation flow is used to circulate the pressure medium gas so that the pressure medium gas inside the hot zone is guided to the outside of the hot zone, the pressure medium gas guided to the outside is joined to the pressure medium gas compulsorily circulated by the first cooling unit so as to cool the pressure medium gas, and a part of the cooled pressure medium gas is returned into the hot zone.
In the hot isotropic pressure device, a part of the pressure medium gas flowing along the first circulation flow is joined to the second circulation flow from the lower side of the hot zone using a fan and an ejector, and the joined pressure medium gas performs a cooling operation while circulating inside the hot zone. Accordingly, a temperature difference caused between upper and lower portions of a furnace during the cooling operation is solved, whereby the inside of the furnace may be efficiently cooled.
In particular, in the container of the hot isotropic pressure device, since the high-temperature pressure medium gas is not directly guided out of the furnace, the inner peripheral surface of the container is not excessively heated. Further, in the compulsory circulation using the ejector, the high cooling speed may be realized. Furthermore, compared to the case where a fan is provided inside the hot zone, the furnace structure is not complex since the ejector without any limit in the type of material concerned with heat resistance or the like is used. Accordingly, there is no concern that the HIP device may increase in cost.
Further, JP 2007-309626A discloses a technique which performs a cooling step in a short time by extracting a pressure medium gas inside a high-pressure container to the outside of the container, cooling the pressure medium gas outside the container, and returning the pressure medium gas into the container.